Lukas,
There's a pull request being discussed right now on GitHub (on my phone, so
you'll have to find it yourself) that might do what you need.
Please head over there and join the conversation.
M
On Tue, 3 Mar 2020, 14:38 Lukas Haase, wrote:
> Hi,
>
> I need to (synchronously) switch the DUC/DDC frequency at certain sample
> intervals.
>
> I previously used the message ports for that and created timed commands.
> This worked nicely for the RX (USRP Source) and with analog retuning.
> However, it turned out that this does not work for the transmitter with
> DUC-only retuning since the DUC/DDC does not have access to the MB clock.
> On the other hand, gr-uhd does not add the sample timing information
> needed. See our discussion in
> http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/2020-March/061615.html
> .
>
> It was suggested to try stream tags and bounce this question on this
> mailing list.
>
> I now use stream tags with USRP Sink with the module below.
> Now the DSP retuning seems to work nicely but ONLY for TX.
> How can I re-tune RX as well?
>
> My approach with the message ports would have allowed me to do both.
> However, stream tags I can only use for "USRP Sink".
>
> Any suggestions are highly appreciated.
>
>
> Best,
> Lukas
>
>
>
>
>
>
>
> PS: This is the code which adds stream tags to retune DUC for USRP Sink:
>
> import numpy as np
> import pmt
> from gnuradio import gr
> from gnuradio import uhd
>
> class blk(gr.sync_block):
> def __init__(self, hop_interval_samples=1000, hop_frequencies=[ 0 1e6
> ]):
> gr.sync_block.__init__(
> self,
> name='Controller',
> in_sig=[np.complex64],
> out_sig=[np.complex64]
> )
> self.hop_frequencies = hop_frequencies
> self.hop_interval_samples = int(hop_interval_samples)
> # state
> self.next_hop = self.hop_interval_samples
> self.current_freq_idx = 0
>
> def work(self, input_items, output_items):
> output_items[0][:] = input_items[0]
>
> window_start = self.nitems_read(0)
> window_end = window_start + len(input_items[0])
>
> while(self.next_hop > window_start and self.next_hop < window_end):
> fcenter = self.hop_frequencies[self.current_freq_idx]
>
> key = pmt.intern("tx_command")
> value = pmt.make_dict()
> value = pmt.dict_add(value, pmt.to_pmt("lo_freq"),
> pmt.to_pmt(900e6))
> value = pmt.dict_add(value, pmt.to_pmt("dsp_freq"),
> pmt.to_pmt(-fcenter))
> self.add_item_tag(0, self.next_hop, key, value)
> self.next_hop = self.next_hop + self.hop_interval_samples
> self.current_freq_idx = (self.current_freq_idx + 1) %
> len(self.hop_frequencies)
>
> return len(output_items[0])
>
>
>
